The invention relates to a gas-permeable, liquid-tight closure, particularly a vented stopper.
In liquid-containing technical installations, e.g. in pipe lines and other liquid-containing apparatus, shutoff devices are often required which prevent the passage of liquids or solids but which should allow the passage of gases, if possible in both directions, i.e. which afford an equalization of pressure.
These shutoff devices are often required in the form of specially constructed closures, such as so-called venting stoppers, also for the closure of storage and transporting containers for liquid or solid substances. In storage or transporting containers for liquid or solid substances, particularly chemicals, excess or reduced pressures may set in after the filling and closing. A reduced pressure may result, for example, by the adsorptive or absorptive bonding of the gaseous phase to the container contents. Excess pressure may form, for example, by the decomposition or degassing of the contents of the container; the decomposition may be accelerated or multiplied due to an accidental or unavoidable elevation of the temperature during transfer or storage and/or due to catalytic effects, of the container material or by foreign matter, for example. The excess or reduced pressures may become so great that it can result in the failure of the closure and/or the container. In order to avoid this, there are known specially constructed container closures, which should enable the degassing of the container. The simplest construction of such a container closure consists of having the closure, e.g. the plug, bored through and having an air line inserted into the bore. Another such closure (German Pat. No. 435,247) consists of a stopper of chemically resistant material, e.g. porcelain, which on the bottom has several openings ending in a hollow space, which is closed from above by a porous filter plate. Furthermore, a safety bottle stopper is known (German Pat. No. 122,472), consisting of a resilient stopper, to be pushed into the bottle mouth, with a cavity or bore and a fine perforation leading toward the interior of the bottle, which is pressed together by the resilient material of the stopper and is closed thereby; when the interior pressure rises beyond a predetermined amount, however, it is opened by the gases for the purpose of bleeding off the excess pressure. Other closures are perforated and have perforated sealing disks. Such closures with perforated sealing disks are also constructed with shaped labyrinth passages. Vent stoppers are also known with spring-loaded valve members, flexible membranes and with prestressed molded parts or material parts in closure combinations.
The known vent stoppers are in part operative only with an upright position of the container. Upon an inclination of the container, a liquid filling may discharge from the closure system, something which is undesirable, depending on the type of contents, might even be dangerous. In order to prevent an escape of the liquid contents from a container on an inclination of the container, closures have been constructed which perform the venting by pendulums or weights only with a normal position of the container. Another vent stopper dependent on position (published German Patent application No. 1,965,519) for liquid containers consists of a stopper with a chamber, which is connected with the interior of the container by a channel and with the atmosphere by an opening. The chamber is partially filled with a liquid metal, normally mercury, and formed in such a manner that the liquid metal closes the channel upon an inclination of the container.
Prior vent stoppers were unsatisfactory either in their manner of functioning or were too cumbersome and expensive in their manufacture.